1. Technical Field
The present invention relates to an input-capable display device, such as, for examples a touch panel, to which an input function is added.
2. Related Art
In recent years, as a compact information electronic apparatus, such as a personal digital assistants (PDA) or a personal computer spreads, a display device that has added a so-called touch panel function, which is used for input operation by bringing an object, such as a finger or a pen, into contact with a display screen, has been widely used. In such a touch panel, there is an electrostatic capacitance method as a method for detecting a position at which a finger, or the like, contacts, which is, for example, described in Japanese Unexamined Patent Application Publication No. 2006-146895 and Japanese Unexamined Patent Application Publication No. 2003-196023. The electrostatic capacitance method is a method that flows a weak electric current through an electrostatic capacitance formed by touching a display surface with user's finger and thereby detects a position of contact on the basis of the amount of electric current. Here, in the electrostatic capacitance method, a detection electrode formed in a planar manner and a dielectric film laminated on the detection electrode are used. By touching the dielectric film with the finger, an electrostatic capacitance is formed.
In a liquid crystal display device with a touch panel function that uses the above electrostatic capacitance method, there is a problem that, when an electric field generated by a driving signal that is supplied between a pair of electrodes for driving a liquid crystal layer reaches the detection electrode, the accuracy of detection of a position of contact is decreased because this electric field component acts as a noise. Here, in the above liquid crystal display device with a touch panel function, it is attempted to remove a noise generated due to a signal that is generated from a driving signal.
In the above existing liquid crystal display device with a touch panel function, however, the following problem still remains. That is, in the existing liquid crystal display device with a touch panel function, there is a problem that it requires a complex system for generating a signal that removes a noise.